Witnessing or being on the receiving end of bullying at work heightens the risk of employees being prescribed antidepressants, sleeping pills, and tranquillisers, finds research published in BMJ Open.

Workplace bullying is linked to poorer mental health among employees, but it is not clear if that translates into a greater need for drug treatment, and if the impact is similar for those witnessing bullying and those who find themselves on the receiving end of it.

The researchers asked 6606 public service employees working for the City of Helsinki in Finland - the largest employer in the country with 200 venues - about their experiences of workplace bullying, both personal and witnessed, between 2000 and 2002.

National registry data on purchases of prescribed "psychoactive" drugs - antidepressants, sedatives, tranquillisers, and sleeping pills - were tracked for three years before the survey and for five years afterwards.

All participants were aged between 40 and 60, and were part of the Helsinki Health Study.

One in 20 employees said they were currently being bullied. A further one in five (18%) women and around one in eight men (12%) said they had been bullied before, either in the same job or in a previous job with another employer.

Around half the respondents said that they had witnessed bullying in the workplace at least occasionally, while around one in 10 said they had witnessed it often.

Women were around 50% more likely to have a prescription for these drugs while men were around twice as likely to do so if they had been bullied at work.

And witnessing workplace bullying had a similar impact. Women were 53% more likely to be prescribed a psychoactive drug, while men were almost twice as likely to receive a prescription of this kind.

The associations remained after taking account of factors likely to influence the results, including previous medication for mental health issues, childhood bullying, social class and weight.

Between one in 10 and one in seven people claim to have been bullied at work in Finland, say the authors, who conclude: "Workplace bullying needs to be tackled proactively in an effective way to prevent its adverse consequences for mental health."